In 2012, BNSF customers reduced their carbon dioxide equivalent emissions (CO2e) by more than 30 million metric tons, the railroad said, noting that's "equivalent to eliminating the consumption and resultant emissions from more than 3 billion gallons of diesel fuel, or 6 million passenger vehicles."

Said BNSF Executive Vice President and Chief Marketing Officer Steve Bobb, "Moving one ton of freight by rail rather than exclusively by truck reduces greenhouse gas emissions by 75%." He added, "BNSF's customers are using rail to create new efficiencies throughout their supply chains to keep their products competitive, to save fuel, reduce their carbon emissions, and relieve highway congestion."

BNSF noted that, for the fifth straight year, it provided its intermodal, automotive, industrial products and agricultural products customers with customized letters that analyzed their total rail carbon footprint savings compared to movement of those shipments exclusively over the highway.

Calculations are based on commodity type and weight, and distance traveled by rail. The calculation also considers the different fuel efficiencies of trailer, container, or carload shipments. The calculation methodology was developed in consultation with Arlington, Va.-basec Clear Carbon Consulting.

BNSF's assessment counters a statement made earlier this week by Pacific Northwest environmental groups, joined by the Sierra Club, threatening to sue BNSF and some of the railroad's coal customers over alleged pollution to regional waterways generated by coal movements.